1. Field of the Invention
The present invention relates to a substrate in which a single crystal semiconductor layer is provided on an insulating layer, and a method for manufacturing the substrate. In particular, the present invention relates to an SOI (silicon on insulator) substrate and a method for manufacturing the same. Furthermore, the present invention relates to a semiconductor device formed using an SOI substrate and a method for manufacturing the same.
2. Description of the Related Art
In recent years, devices such as semiconductor integrated circuits, which use an SOI substrate including a thin single crystal semiconductor layer formed on an insulating surface, have been developed instead of those using a bulk silicon wafer. Since the parasitic capacitance between a drain of a transistor and a substrate is reduced by using an SOI substrate, SOI substrates have attracted attention as substrates for improving the performance of devices.
One of the known methods for manufacturing an SOI substrate is Smart Cut (registered trademark) method (see Patent Document 1, for example). An outline of the method for manufacturing an SOI substrate by Smart Cut (registered trademark) method is described below. First, hydrogen ions are implanted into a silicon wafer by an ion implantation method so that an embrittled region including a defect is formed at a predetermined depth from a surface. Then, the silicon wafer into which hydrogen ions have been implanted is bonded to another silicon wafer with a silicon oxide film interposed therebetween. After that, heat treatment is performed so that a part of the silicon wafer into which hydrogen ions have been implanted is separated in a thin film shape along the embrittled region. Thus, a single crystal silicon film can be obtained over the other bonded silicon wafer. Smart Cut (registered trademark) method is also referred to as a hydrogen ion implantation separation method.
A method has also been proposed in which a single crystal silicon layer is formed over a base substrate made of glass by such Smart Cut (registered trademark) method (see Patent Document 2, for example). Glass substrates can have a larger area and are less expensive than silicon wafers, and thus are mainly used for manufacturing liquid crystal display devices and the like. By using a glass substrate as a base substrate, a large, inexpensive SOI substrate can be manufactured.
[Reference]
[Patent Document]
    [Patent Document 1] Japanese Published Patent Application No. H05-211128    [Patent Document 2] Japanese Published Patent Application No. 2005-252244